The present invention relates to an image pickup control method and image pickup device using an image pickup element, such as a CCD, and operable in a plurality of image pickup modes with different resolutions.
FIG. 7 is a block diagram showing an arrangement of a conventional image pickup device having a plurality of image pickup modes.
Here, a description will be made in terms of an arrangement and operation of an image pickup control system. An image signal, outputted from an A/D converting section 5, is inputted into an image pickup control section 22. In the image pickup control section 22, an image pickup control constant calculating section 22a calculates image pickup control constants, for example, such an evaluation value for automatic focusing control as a peak value of a luminance signal within a given frame region of an image signal and a difference value between the maximum and minimum luminance values of a line, such an evaluation value for automatic aperture control as a differential value of a luminance signal within a given frame region, and such an evaluation value for automatic white balance control as an integral value of a luminance signal within a given frame region and an integral value of a color-difference signal. These image pickup constant values depends on arrangements of an image pickup optical system and processing system, and this specification does not limit them to a particular value.
On the basis of these constant values, control is made in terms of, for example, a focusing lens (included in an optical lens 1) for providing an optimal focus, an aperture 2, shutter speed (an optical charging time of an image pickup sensor 3) and a gain (a gain of an SH/AGC section 4) for offering an optimal exposure, and a color correction (a correction for first and second color processing sections 7, 12) for regulating the white balance.
In addition, in accordance with an instruction from a system control section 23 depending on an input from an operation section 24, there are carried out the image pickup mode switching control, i.e., the operation of a change-over switch 6 for a signal processing system, the operation of a change-over switch 20 for a synchronizing signal generator, the manual setting of various image pickup control constants, and so on.
Furthermore, a description will be made in terms of the operation of the image pickup control section 22 with reference to an operational algorithm of FIG. 6. A decision is first made as to whether a first or second mode is taken as the image pickup mode (step S001, which will be referred hereinafter to as S001). When taking the first image pickup mode, the image pickup control constant calculating section 22a calculates an image pickup control constant for the first image pickup mode (S002), and sets the image pickup mode change-over switches 6, 20 to the first image pickup mode side (S003). Then, the control output for an image pickup system is made on the basis of the image pickup control constants (S004).
On the other hand, in the second image pickup mode, a still picture is first temporarily image-picked up (S005), and the image pickup control constants for the second image pickup mode are then calculated in the image pickup control constant calculating section 22a (S006). The same process is done in terms of n still pictures (S007). This n is indicative of the number of pictures necessary for the determination of the image pickup control constants in the second image pickup mode and takes an integer of 1 or more. After the completion of the calculation, the image pickup mode change-over switches 6, 20 are set to the second image pickup mode side (S008) before the control output for the image pickup system is made on the basis of the image pickup control constants (S009). This state is maintained until the switching instruction to the first image pickup mode is given (S010).
However, there are the following problems which arise with such a conventional apparatus. That is, the first disadvantage is that, when the change-over is made from the first image pickup mode (for example, a video rate) to the second image pickup mode (for example, a high-resolution still picture rate), the image pickup control constants for the second image pickup mode are required to be newly calculated from the beginning, whereby pictures (n pictures) need to be in advance taken several times. A long time is required for taking or receiving the high-resolution images in the second image pickup mode, and therefore the normal images cannot be taken immediately after the change-over to the second image pickup mode.
The second disadvantage is that, when a still picture is taken during the operation in the first image pickup mode, the user is needed to carry out the change-over of the image pickup mode, the decision as to whether or not to complete to take the still picture, and the change-over to the original image pickup mode. Thus, the user has to pay attention to these operations until completing to take the still picture.